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Primary Secondary Loop Alternate Set Up

asked 2015-03-26 16:33:24 -0600

pflaumingo gravatar image

updated 2015-08-14 10:44:45 -0600

I was wondering if it is possible to set up primary-secondary loops on one plant loop by having the primary pumps be in parallel branches on the supply side and then placing a secondary pump in series on the demand side just after the demand inlet node.

I know primary secondary loops have been addressed before in this forum here and I too would use that set up normally, especially as I've heard that the common pipe object is being made obsolete in EnergyPlus.

However, the new California compliance "engine" automatically generates an OSM file and for primary secondary loops produces the loops as described.

CBECC-COM generated Primary Secondary

I was wondering if perhaps there is a quirk to EnergyPlus that makes this a valid modeling schematic?

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Here are your ten points. Are you talking about CBECC-Com?

Julien Marrec gravatar image Julien Marrec  ( 2015-03-26 17:33:58 -0600 )edit

Yup, have a bunch or advanced systems that I can't model in CBECC-Com natively. I've just taken a look at the IDF file and it looks like it implements the common pipe simulation on the PlantLoop object. Does anyone know how to do this in OS? Or have they most likely implemented it through a measure or the API?

pflaumingo gravatar image pflaumingo  ( 2015-03-26 17:57:30 -0600 )edit

Welcome and +1 for your terrific MS Paint skills :) (I'm removing the greetings from your post according to this, nothing against you!)

Julien Marrec gravatar image Julien Marrec  ( 2015-03-26 18:04:53 -0600 )edit

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answered 2015-03-27 09:24:20 -0600

It is possible to setup primary secondary systems with a single plant using the built in common pipe model of PlantLoop. OpenStudio supports this feature programmatically and the CBECC engine is in fact making use of this feature. The key is setting up the model the way your schematic shows AND also setting the "Common Pipe Simulation" property of PlantLoop to common pipe. We generally discourage this approach although it is proven to work in the configurations that CBECC supports (no variable speed branch pumps). In an effort to steer you in the direction described here we have explicitly hidden the "Common Pipe Simulation" in the OpenStudio Application. Models coming out of CBECC will have the common pipe enabled, but you wont be able to manipulate this property in the OpenStudio application. You can however use an OpenStudio Measure to programmatically set the common pipe simulation using this method.

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Hi Kyle, I did setup pri-sec loops with a single plant and also added the HX object for WSE purpose onto the CHW and CW loops. And the WSE was performed very well. However, I separated the primary and secondary loops with HX object with two plant loops. I also added the new HX object to CHW and CW loops for WSE but the WSE doesn't do anything at all even though I have the same setup as it was in the single plant loop ....what did I do wrong?

PM gravatar image PM  ( 2016-09-13 12:15:18 -0600 )edit

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Asked: 2015-03-26 16:33:24 -0600

Seen: 623 times

Last updated: Mar 27 '15